Measuring instrument



Nov. 21; 1939. H. A. HENiE 2,130,588

MEASURING INSTRUMENT Filed: Jan. 15. 1936 2 Sheets-Sheet 1 INVENTOR HUEERT 6. HENZE ATTORNEYS H-A. HENZE MEASURING INSTRUMENT Filed Jan. 15, 1936 Nov. 21, 1939.

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Patented Nov. 21, 1939 UNITED, STATES PATENT-,- OFFICE p MEASURING-INSTRUMENT Hubert A. Henze, Wood-Ridge, N. J. Application January 15, 1936, Serial No. 59,192

I zolaims. .(01. 201-48)' This invention relates to measuring instruments and more particularly to measuring instruments which are responsive to pressure. The

invention may be embodied-in a depth gauge, a pressure gauge, avacuum gauge, or any other instrument in which the condition to be measured and indicated produces pressure or may be caused to produce pressure.

It is an object of the invention to provide a pressure responsive unit which is sensitive and accurate and which has a long range of movement,-,in combination with electrical means protected and directly actuated by the unit without the necessity of interposed gearing. It is a feature of theinvention'that the electrical means is in part housed and protected by the pressure responsive unit. It is not, however, necessary to house the electrical means within the pressure responsive unit may be transmitted to theelectrical unit by means of a rod or other mechanical device.

In accordance with preferred embodiments 01 the invention the pressure responsive element is a flexible metallic bellows, and provision'is made l within the bellows of a rheostat or. other electrical unit controlled by the bellows, and in turn controlling the impedance of an indicator circuit.

With such an arrangement not only is the electrical apparatus protected from contact with oil,

water or other extraneous and harmful substances, but contact of oil or water is limited to the exterior of the bellows. The unit is made readily removable so that it can be taken .out and cleaned from time to time and thereby maintained in a condition to operate sensitively and accurately over a prolonged period of use. In every instancenivhere the bellows may be exposed to a pressure greater than atmospheric pressure, it is important that the pressure be applied externally to the bellows. With such an arrangement, excessive pressure cannot burst the bellows but can only collapse it, so that no injury can result.

Other objects and advantageswill hereinafter appear.

in the drawings forming, part of this specification,

Fig. 1 is a view of a depth gauge embodying features of the invention installed in a tank;

Fig. 2 is a fragmentary vertical sectional view on a larger scale than 1 showing details of mounted outside of the pressure responsive unit,

construction of the pressure responsive unit of Fig. 1; Fig. 3 is a horizontal sectional view taken on the line 3-3 of Fig. 2 looking in the direction of the arrows;

Fig. 4 is a view in elevation of the pressure responsive unit of Fig. 2 with a diflerent type of outer housing or shell applied to adapt the instrument to be employed as a pressure gauge; Fig. 5 is a view similar to Fig. 2 illustrating a modified embodiment in which the instrument is used as a control device for maintaining pressure within pre-determined limits;

Fig. 6 is a view similar to Fig. 2 illustrating a further modified form of instrument adaptedto be used as a vacuum gauge; and

Fig. '7 is an electrical diagram illustrating a. suitable wiring arrangement for the instrument of the figures othertha-n Fig. 5.

In the embodiment of Figs. 1 to 3 and 7 a pressure responsive device I is desirably located in the bottom of a tank 2 containing liquid whose depth or volume is to be indicated. The tank may be either above the ground or buried since the instrument is adapted to be introduced through the top of the tank and to be located within the tank. A pipe line '3 is in sealed communication with the exterior of the device I and serves as a conduit for protecting electrical wires which lead, from the device I to a source of current and to an indicating instrument 4. The instrument 4 is desirably of the type known as a diiferential volt meter and may be made like the instrument disclosed in United States Letters Patent to F. I. and B, P. Remy and A. Berger, No. 1,189,869, for Liquid gauge dated July'4, 1916.

The pressure responsive device I comprises :n outer protective shell or housing 5 having perforations 6 and I through its sides and bottoms, respectively, to permit the free ingress and egress of liquid. The shell 5 is secured in any suitable manner as by screws 8 to a head block 9. The block 9 includes a threaded boss I0 to which .a flexible metallic bellows II is detachably secured by means of a threaded ring I2. The block 9 has secured to its lower side a pair of blocks or cylinders l3 of insulating material upon which coils I4 of flne resistance wire are wound. Each block I3 surrounds the shank of a long screw I5 which isthreaded into the boss III of the block 9. On the shank of each screw below the block I3, there are provided successively a metallic ring I6 and an insulating ring II. The rings I6 are conductively connected to the coils I4 and to one another so that the circuit is never open. Thus there is never any possibility of arcing in case. the sliding contact for any reason makes poor contact with one of the coils or leaves engagement with one of the coils. A

5 metallicyoke 1-8 extends across to underlie both;

insulating rings l1 and to be impaled upon both screws IS. The yoke member I8- imparts rigidity and stability to thestructure.

up and down along the coils. Increased ex-'- ternal pressure applied to the bellows causes the stem 'l9 and the contact 22 to move upward while a reduction oi. external pressure permits the b ows to expand'and to draw the contact 22 do ward. The upper end of the stem I9 is guided in an axial bore 23 formed in' a long screw 24 which. isthreaded through the boss 25 ll! of the block 9. A compression coil spring 25 is interposed between the contact ca rier 2| and the screw 24 and encircles thgfizem l9. Because oi. unavoidable irregularities the manufacture of the bellows it is desirable 0 provide some adjustment for bringing the response of the pressure deviceinto' coordination with the scale of the indicating instrumentl. The adjustable nut 24 and the spring 25 serve this function. Thus, if the bellows as made is stiffer than the standard intended the screw 24 will be adjusted so as to apply a relatively slight pressure to the contact carrier 2|,but if the bellows is more flexible'and yielding than intended the screw 24 will be adjusted so as to apply a relatively great pressure of the spring 25 and thus compensate for the lack of resistance to compression of the bellows. r I

The upper end of each coil I4 is connected to aconductive collar 26 mounted onthe associated block is and the collars are connected'respectively to conductors 21 and 28. The conductors 21 and .28 extend upward through bores provided in theboss l0 and thence through a bored fitting 28. The fitting 29 is removably threaded in a 5 threaded bore 30 in the upper-portion ofthe block '0. When calibrating the instrument by means of the screw 24 the fitting 29 is desirably unthreaded from the block 3, the arrangement being such that the screw 24 may be conveniently made accessible. The fitting 23 is provided with diametrically opposed recesses 30' to enable the fitting to be turned by means of a spanner wrench. A pipe 3| extends upward from the fitfing through a plug 32 in the top of a tank. The protective housing formed by the pipe 3| may be continuedthrough any suitable series of pipes and fittings. The pipe or tubing communicating with it is open to the atmosphere at the exterior of the tank sothat atmospheric pressure exists at all times within the bellows; 'The pipe serves as a vent for. the interior of the bellows. Removal of the plug 32 from the top .of the tank enables the entire rinstrument to be withdrawn. A suitable electrical circuit of the instrument described is diagrammatically illustrated in Fig.

'7. One terminal of a suitable source of current, such as an ordinary doorbell transformer, is. connected through a conductor 33 directly with the indicating 4, the current travers-' I It also serves asa guide for a stem l9 which is. both ing one of the two itngulafrly related windings oi the instrument and returning to the source through a conductor 34. A branch conductor 35 runs from the conductor 33 to one of the windingsv I4. Thecurrent passes thence across 5 the bridging contact 22 to the other winding 14, fiows to the instrument 4 through a conductor 36 and passes through the second of the angularly related coils of the instrument 4 to the conductor 34. As is well understoodthe coils of 10 the instrument 4 act in opposed relation upon a common armature whereby the pointer 31 is carried. The position of the pointer is a function of the relative magnitudes of the electromagnetic force exerted by the instrument coils. 15 and not of the absolute values of such forces. The instrument, is therefore independent of source variations of potential. Because of the fact, however, that the bridging contact 22 cuts out more or less turns of the rheostat coils i4 20 according to the degree of compression of the bellows,.the impedance of the circuit including one of the coils is varied, while the impedance of the circuit including the other coil is constant. The position of the pointer is caused therefore to 25 be a function of the pressure exerted upon the bellows.

The instrument as described has been found to be very simple and economical to manufacture and very accurate and efilcient in use; 30 being sensitively responsive to very slight changes of liquid level.

The embodiment of Fig. 4 is similanin all respects to the embodiment of Figs. 1 to 3 with the exception that a casing 5a of a construction someas what different from the casing 5 is provided. This .instrument is designed to be used as'a pressure e change virithe casing g. 4 'is in all respects identical with the instrument of Figs. 1 to 3 and the same reference .num'erals have accordo ingly been applied with the subscript a added. The strength of the spring is chosen in accordance with the pressure range to be measured.

The instrumentof Fig. 5 is generally the same as that of Fig. 4. The instrument has been modi- 55 fled, however; to adapt it to open an electrical circuit'when a pre-determined pressure range is exceeded and to close the circuit when the pressure falls below such pre-determined range.- In

circuit is energized for closing a compressor mo- 70 tor circuit. The motor circuit remains closed until the sliding "contact 22b engages the contact 40, whereupon a second relay circuit is energized to open the compressor motor circuit.

The motor controlling contacts as shown in u Fig. may be employed in combination with a rheostat and indicating instrument if desired so that the pressure responsive mechanism serves both to give an indication to the attendant and to automatically control the pump motor.

In the form of the invention disclosed in Fig. 6 the arrangement is generally similar to that of 1 1g. 4. The instrument of Fig. 6, however is adapted to act asa vacuum gauge, the sliding contact 220 being arranged to engage the upper ends of the coils ilc when the external and internal pressures are equal and to move downward along the coils as the vacuum in the casing 5c increases, that is to say, as the absolute pressure in the casing 50 diminishes. In this instance the spring 250 is a tension spring which is connected at its upper end to the bored screw 0. Since rotation of the screw 24c involves a turning of the spring provision is made to permit the spring to be turned freely with the screw. The lower end of the spring 250 is accordingly connected to a collar 4| which encircles the rod I90 and which is provided with a radial pin 42 that extends into a circumferential groove 3 of the rod. The pin 42 and the groove 43 cause the collar 4| to move longitudinally in unison with the rod 190, but permit the collar to turn freely relative to the rod I90.

The parts are otherwise the same as in the embodiment of Fig. 4 and hence corresponding reference numerals have been applied with the submript 0 added.

While I have illustrated and described in detail certain preferred forms of my invention, it is to be understood that .changes may be made therein and the invention embodied in other structures. I do not, therefore, desire to limit myself to the specific constructions illustrated, but intend to cover my invention broadly in whatever form its principle may beeutilized.

I claim:

1. In a pressure responsive instrument, in combination, an elongated, circumferentially corrugated, cylindrical bellows, a fitting supporting one end of the bellows stationary, but permitting the opposite end to move in response to pressure variations, said fitting cooperating with the bellows to provide a chamber completely sealed against ingress of the surrounding medium, electrical impedance means supported from the fitting within the bellows, a stem within the bollows connected to the movable end of the bellows, a sliding' contact carried by said stem, a plug threaded through the fitting, said plug containing an axial bore of slightly larger diameter than the stem and through which the stem slides, and a spring interposed between the plug and the sliding contact, said spring being adjustable by turn v ing of the threaded plug.

2. In a pressure responsive device, in combination, a circumferentially corrugated, cylindrical bellows, a hollow fitting supporting one end of the bellows stationary but permitting the other end to move in response to pressure variations, said fitting cooperating with the bellows to provide a chamber completely sealed against ingress of the surrounding medium, a stem within the bellows connected to the movable end thereof, a plug screwed in the fitting having an axial bore of slightly greater diameter than the stems through which the stem slides, for guiding the stem against lateral movement, a compression spring surrounding the stem, one end of which abuts against the plug and the other end of which moves in accordance withthe pressure induced movement of the bellows, tension of said spring being adjustable by turning the plug, and variable electrical impedance means, one member thereof being mounted in fixed relation to the fitting and a movable member thereof being mounted upon said stem in cooperative relation with said fixed member.

' HUBERT A. HENZE. 

